She rose to fame for her role as Sarah Reeves Merrin on the Fox teen drama Party of Five (1995–99).
She played Pierce Brosnan's daughter in a pilot for NBC called Running Wilde (1993), which featured Brosnan as a reporter for Auto World magazine, whose stories cover his own wild auto adventures.
In addition to acting, she has served as a producer on some of her film and television projects.
As a singer, Hewitt has been signed by Atlantic Records and Jive Records, and is primarily known for her recordings in the pop genre.
She appeared in the sequel I Still Know What You Did Last Summer (1998), which, though not as successful as the first film, took in more money on its opening weekend.
She was nominated for a Golden Globe Award for the pilot movie.From 2014 to 2015, she starred as Special Agent Kate Callahan on the CBS crime drama Criminal Minds.